The invention provides a global optimization and dispatching method based on time scales. The method uses a target value system and a dispatch model. The global optimization and dispatching method takes input from the results from a variety of subtopics. The methods provide adjustment and optimization in accordance with the time scales that are given in the sub goal of each sub topic: long-term, mid-long-term, short-term, ultra short term and real time optimization. Smart distribution grid can improve operational efficiency, integrated application of new elements in the distribution network of distribution energy network, micro grid, energy storage device and non-linear loads. This invention is fully adapted to the smart grid trends, with a good prospective.